The far side of the moon sails across Earth in new NASA video
The far side of the moon sails across the brightly lighted disk of the Earth in this new series of images from NASA.
The pictures were taken between 12:50 p.m. and 5:45 p.m. PDT on July 16, and they show the moon moving across the Pacific Ocean and America.
They were taken by an instrument aboard the Deep Space Climate Observatory, or DSCOVR, satellite that orbits the sun at a distance of 1 million miles from Earth.
DSCOVR will take similar images about twice a year when the satellite moves across the orbital plain of the moon. But since it just arrived at its new home earlier this summer, these are the first of these images that have been sent back to Earth.
From the vantage point of our planet we see only one side of the moon, but these images were taken from a satellite located between the Earth-moon system and the sun.
The dark gray disk that you see progressing across our blue planet is the part of the moon that cannot be seen from Earth.
"The lunar transit is the back side of the moon — very different looking than the familiar face -- no man in the moon, no mares, no cheese," said Adam Szabo, a heliophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md.
He said he was initially surprised by how dark the moon looked against the bright technicolor of the Earth.
"From my perspective here on Earth the moon looks very bright in the sky so it surprised me that the Earth is that much more brilliant," he said.
Of course, the difference in brightness makes sense if you think about it a bit. Both objects in the image are receiving the same amount of light from the sun, but the powdery regolith that covers the surface of the moon is not as reflective as the surface of the Earth, which is largely water.
"Water is rather reflective almost like a mirror, so it shouldn’t be a surprise," he said. "The earth is a shinier, better reflecting object."
DSCOVR's primary objective is to keep an eye on the constant stream of particles that emanate from the sun, known as the solar wind. In particular, it is looking for large outbursts of material known as coronal mass ejections that could affect power grids, aviation and other important technologies on and around Earth.
From its vantage point 1 million miles upstream of our planet, instruments aboard DSCOVR can detect incoming CME's 30 to 45 minutes before they strike the Earth's atmosphere. That gives technology companies a bit of time to protect their instruments.
The pictures above were taken by an instrument dedicated to DSCOVR's secondary objective -- the monitoring of Earth. The EPIC instrument snaps images of the planet in 10 wavelengths of light that allow scientists to see how ozone is distributed in our atmosphere, how many aerosols are floating around, and where leafy plants are among other measurements.
These observations are currently being made by satellites closer to the planet, but DSCOVR's distance from Earth allows it to see how these wavelengths change from sunrise to sunset at the same spot on Earth. That is a measurement that has never been able to be made before.
DSCOVR is still getting used to its new home in deep space. Szabo said it will take a few more months of testing and calibrating the instruments before scientific measurements can be made. But in the meantime, the team has been able to release spectacular images of the Earth by combining three of the wavelengths of light that EPIC observes.
In this case, the moon happily got in the way.
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